linux-kernel - checkpatch false warning. was: [PATCH 3/5] mm, page_owner: copy page owner info during migration

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Date:	Wed, 4 Nov 2015 16:10:07 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Andy Whitcroft <apw@...onical.com>, Joe Perches <joe@...ches.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: checkpatch false warning. was: [PATCH 3/5] mm, page_owner: copy page
 owner info during migration

On 11/04/2015 04:00 PM, Vlastimil Babka wrote:
> The page_owner mechanism stores gfp_flags of an allocation and stack trace
> that lead to it. During page migration, the original information is
> essentially replaced by the allocation of free page as the migration target.
> Arguably this is less useful and might lead to all the page_owner info for
> migratable pages gradually converge towards compaction or numa balancing
> migrations. It has also lead to inaccuracies such as one fixed by commit
> e2cfc91120fa ("mm/page_owner: set correct gfp_mask on page_owner").

Hi,

This patch gives me the following checkpatch warning:

ERROR: Please use git commit description style 'commit <12+ chars of sha1> ("<title line>")' - ie: 'commit e2cfc91120fa ("mm/page_owner: set correct gfp_mask on page_owner")'
#12: 
e2cfc91120fa ("mm/page_owner: set correct gfp_mask on page_owner").

Some fuzzing showed that it's complaining about the missing word "commit"
which is however on the end of the previous line. Can that be fixed please?
I can't speak perl myself.

Thanks,
Vlastimil
 
> This patch thus introduces copying the page_owner info during migration.
> However, since the fact that the page has been migrated from its original
> place might be useful for debugging, the next patch will introduce a way to
> track that information as well.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>   include/linux/page_owner.h | 10 +++++++++-
>   mm/migrate.c               |  2 ++
>   mm/page_owner.c            | 16 ++++++++++++++++
>   3 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
> index 8e2eb15..6440daa 100644
> --- a/include/linux/page_owner.h
> +++ b/include/linux/page_owner.h
> @@ -11,6 +11,7 @@ extern void __reset_page_owner(struct page *page, unsigned int order);
>   extern void __set_page_owner(struct page *page,
>   			unsigned int order, gfp_t gfp_mask);
>   extern gfp_t __get_page_owner_gfp(struct page *page);
> +extern void __copy_page_owner(struct page *oldpage, struct page *newpage);
>   
>   static inline void reset_page_owner(struct page *page, unsigned int order)
>   {
> @@ -32,6 +33,11 @@ static inline gfp_t get_page_owner_gfp(struct page *page)
>   	else
>   		return 0;
>   }
> +static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
> +{
> +	if (static_branch_unlikely(&page_owner_inited))
> +		__copy_page_owner(oldpage, newpage);
> +}
>   #else
>   static inline void reset_page_owner(struct page *page, unsigned int order)
>   {
> @@ -44,6 +50,8 @@ static inline gfp_t get_page_owner_gfp(struct page *page)
>   {
>   	return 0;
>   }
> -
> +static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
> +{
> +}
>   #endif /* CONFIG_PAGE_OWNER */
>   #endif /* __LINUX_PAGE_OWNER_H */
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 1ae0113..9f82e03 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -38,6 +38,7 @@
>   #include <linux/balloon_compaction.h>
>   #include <linux/mmu_notifier.h>
>   #include <linux/page_idle.h>
> +#include <linux/page_owner.h>
>   
>   #include <asm/tlbflush.h>
>   
> @@ -775,6 +776,7 @@ static int move_to_new_page(struct page *newpage, struct page *page,
>   		set_page_memcg(page, NULL);
>   		if (!PageAnon(page))
>   			page->mapping = NULL;
> +		copy_page_owner(page, newpage);
>   	}
>   	return rc;
>   }
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 7664b85..7ebd3d0 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -84,6 +84,22 @@ gfp_t __get_page_owner_gfp(struct page *page)
>   	return page_ext->gfp_mask;
>   }
>   
> +void __copy_page_owner(struct page *oldpage, struct page *newpage)
> +{
> +	struct page_ext *old_ext = lookup_page_ext(oldpage);
> +	struct page_ext *new_ext = lookup_page_ext(newpage);
> +	int i;
> +
> +	new_ext->order = old_ext->order;
> +	new_ext->gfp_mask = old_ext->gfp_mask;
> +	new_ext->nr_entries = old_ext->nr_entries;
> +
> +	for (i = 0; i < ARRAY_SIZE(new_ext->trace_entries); i++)
> +		new_ext->trace_entries[i] = old_ext->trace_entries[i];
> +
> +	__set_bit(PAGE_EXT_OWNER, &new_ext->flags);
> +}
> +
>   static ssize_t
>   print_page_owner(char __user *buf, size_t count, unsigned long pfn,
>   		struct page *page, struct page_ext *page_ext)
> 

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